QS-650 full section ballast cleaning machine is designed to dig out, without the removal of track skeletons, the ballast under the track skeleton by means of the motion of its excavation chain, and it allows the ballast dug out to be screened by its vibrating screen. The dirt will be conveyed to the two sides of the railway in front of the machine or back to the material conveyor truck, while the clean ballast will be backfilled into the railway median directly or backfilled into the ballast bed at the two sides of the steel track behind the excavation chain by means of its backfilling conveyor belt. Due to the even backfilling of ballast over the whole section of railway track, the machine can reduce the work quantity of track tamping. For track sections subject to slurry pumping, the machine also can perform complete cleaning of ballast.